The investigations proposed herein are designed to determine if the bullous skin diseases of man, in particular pemphigus, bullous pemphigoid and herpes gestationis, are immunologic diseases mediated by the complement system and immune complex formation. Considerable evidence, detailed here, suggests that they are, but many fundamental questions, including how the complement system is activated, are immune complexes found in all of these diseases, and what relationship complement activation and immune complex formation has to disease production, must be still determined. The role of the properdin system in these diseases also must be clarified. Other immunologic cutaneous diseases, in particular cutaneous lupus erythematosus and vasculitis, will also be investigated. The pathology of these cutaneous diseases is so accessible to study, that fundamental questions as to how complement activation and immune complexes participate in local immunologic injury may become apparent as well. BIBLIOGRAPHIC REFERENCES: Jordan, R.E., Schroeter, A.L., Good, R.A., Day, N.K.: The Complement System in Bullous Pemphigoid. II. Immunofluorescent Evidence for Both Classical and Alternate-Pathway Activation. Clin. Immunol. Immunopath. 3:307-314, 1975. Schroeter, A.L., Diaz-Perez, J.L., Winkelmann, R.K., Jordon, R.E.: Livido Vasculitis (The Vasculitis of Atrophie Blanche): Immunopathologic Study. Arch. Derm. 111:188-193, February 1975.